Natural History of Volcanos and Earthquakes. 67 



and EniSj which rise in deeply hollowed valleys in clay-slate 

 rocksj are thus produced. 



We may also easily conceive the possibility of obtaining a 

 thermal spring by boring. A slight glance at the figure will show 

 that a hole bored into a clay-slate rock in a valley, in the vicinity 

 of a volcanic cone, will probably give exit to a thermal spring, if 

 the borer reach the surface of a stratum or a slate surface com- 

 municating with the cleft between the volcanic and the clay- 

 slate rock. A successful attempt of this kind was actually made 

 a few years ago, by boring into the clay-slate rock at the foot of 

 the basaltic hill, the Landskrone in the Alir valley, about three 

 German miles north of the Laacher See^ when a copious mineral 

 was obtained of the temperature of 58^ F., affording consider- 

 able disengagement of carbonic acid gas. Indications prognosti- 

 cating a favorable result of this undertaking were indeed pres- 

 ent, inasmuch as a mineral spring already existed at the distance 

 of but a few steps from the spot.* 



Phenomena, perfectly resembling those which are observed 

 where volcanic masses have actually broken through, present 

 themselves very frequently. A cleavage, reaching to great depths, 

 may also be a consequence of a preceding elevation and fracture 

 of the component strata, without an actual breaking through 

 having taken place. Tliese phenomena are found in formations 

 of all ages. Thus Hoffmannf has pointed out, in the north- 

 west of Germany, some i^culiar valleys which, originally per- 

 fectly closed, are surrounded on all sides by a precipitous escarp- 

 ment, whose component strata incline from the centre downward, 

 in every direction. He has given to these valleys the name of 



* A joint-stock company is also at this moment employed in boring into clay- 

 slate rock at Thal-EhretibreU^tela, near CoblttUz, in order to procure thermal 

 springs. Since this spot lies scarcely two German miles distant from the well- 

 known hot springs of the temperature of 75° to ISl'^ F. at Ems, and at a lower 

 level, and since an acidulous spring already exists there, the possibility of the sue- 

 cess of this undertaking is as little to be despaired of, as a favorable result can be 

 promised. Leop. von Buchs remarks on this subject in Aoggeraths Ausflug nach 

 Boh .en Bonn 1838, p. 5. The instance of the salt work of Xauenhcim, near 

 Friedberg where a sail spring of 100^ F. with immense disengagement of carbonic 

 acid gas was obtained by boring, proves that success is more likely to attend by 

 boring into secondary formations, where a more frequent alternation ot various 

 strata exists. At Hofgelsmar, near Cassd, a new thermal spring with copious dis- 



engage 



ment of carbonic acid gas was also obtained by boring, in May, 1834, 



1 PoggendorflTs Ana. t. xvii, p. lol. 



